The dyeing of keratin fibers, such as human hair, with dyeing compositions containing oxidation dye precursors, generally called oxidation bases, such as ortho- or para-phenylenediamines, ortho- or para-aminophenols and heterocyclic compounds, is known. These oxidation bases are colorless or weakly colored compounds, which when combined with oxidizing products can give rise, by a process of oxidative condensation, to colored compounds.
It is also known that it is possible to vary the shades obtained with these oxidation bases by combining them with couplers or dyeing modifiers, the latter being chosen, for example, from aromatic meta-diaminobenzenes, meta-aminophenols, meta-diphenols and some heterocyclic compounds, such as indole compounds and pyridine compounds.
The great variety of the molecules employed for the oxidation bases and the couplers means that a rich palette of colors can be obtained.
The so-called “permanent” dyeing obtained using these oxidation dyes should ideally, in addition, satisfy at least one of a number of requirements. Thus, it ideally has no problems of a toxicological nature, makes it possible to obtain the color shades of the desired intensity, has good resistance to external agents such as light, weather, washing, permanent waving, sweat and rubbing, provides coverage of white hair, and/or displays minimum selectivity, i.e., ensures that the smallest possible differences in coloration are obtained all the way along the same keratin fiber, which generally is differently sensitized (i.e., damaged) between its tip and its root.